Twenty-five CHF patients underwent polysomnography with simultaneous beat-to-beat blood pressure (Portapres), respiration and electrocardiogram monitoring. Patients were divided according to the presence (SA, n = 17) and absence of SA (NoSA, n = 8). Power spectral analyses of heart rate variability (HRV) and spontaneous baroreflex sensitivity (BRS) were determined in periods with stable breathing while awake at 6 am, 10 am, 10 pm, as well as during stage 2 sleep. In addition, muscle sympathetic nerve activity (MSNA) was evaluated at 10 am.
RR variance, low-frequency (LF), high-frequency (HF) powers of HRV, and BRS were significantly lower in patients with SA compared with NoSA in all periods. HF power, a marker of vagal activity, increased during sleep in patients with NoSA but in contrast did not change across the 24-hour period in patients with SA. MSNA was significantly higher in patients with SA compared with NoSA. RR variance, LF and HF powers correlated inversely with simultaneous MSNA (r = − 0.64, − 0.61, and − 0.61 respectively; P < 0.01).
Patients with CHF and SA present a reduced and blunted cardiac autonomic modulation across the 24-hour period. These findings may help to explain the increased cardiovascular risk in patients with CHF and SA.